1. Field of the Invention
The present invention relates to a touchscreen.
2. Description of the Background Art
A touch panel is an apparatus that detects a touch with a finger or the like and specifies the positional coordinates of the touched position. The touch panel is receiving attention as one of excellent user interface means. The touch panels of various types, such as the resistive type and the capacitive type, are commercially available.
Generally, a touch panel is structured by a touchscreen in which a touch sensor is built, and a detecting apparatus that specifies the positional coordinates of a touch based on a signal from the touchscreen.
The capacitive touch panels include a projected capacitive touch panel (for example, see Japanese Patent Application Laid-Open No. 2012-103761).
The projected capacitive touch panel is capable of detecting a touch even when the front side of the touchscreen in which the touch sensor is built is covered by a protective plate, such as a glass plate whose thickness measures several millimeters.
The touch panel of this type is advantageously robust because the protective plate can be arranged on the front side. Further, a touch can be detected even when it is made with a gloved finger. Still further, it is long-life because no movable portion is included.
The projected capacitive touch panel specifies the positional coordinates of a touch by detecting a change in the electric field between a plurality of row-directional lines provided to extend in the row direction to form a first electrode and a plurality of column-directional lines provided to extend in the columnar direction to form a second electrode, that is, a change in cross-capacitance. This detection scheme is generally referred to as the mutual capacitance detection type (for example, see Japanese Unexamined Patent Application Publication (Translation of PCT Application) No. 2003-526831).
Further, in the case where a touchscreen is attached to a display apparatus, the displaying area of the display apparatus is covered by the row-directional lines and the column-directional lines of the touchscreen. Since the transmission of the displaying light or the reflectivity of external light becomes non-uniform depending on the arrangement of the lines, the moire phenomenon may occur or the lines may be visually recognized. In order to provide the user with images of high quality, a touchscreen whose presence is less noticeable for the user, such as those with lines being less visually recognizable, is preferable.
The projected capacitive touch panel described above involves the following problem: when the electric field coupling between the first electrode and the second electrode is great, a change in cross-capacitance do not easily occur when the touch panel is touched by a pointer such as a finger, making it impossible to secure high detection sensitivity. Setting low detection sensitivity, erroneous detection tends to occur.